I personally don't think that a sequel to Avatar would be that exciting without Pandora. All the lush landscape and nature of Pandora made me want to live there forever, not to mention all of Pandora's inhabitants. Since Avatar kind of revolves around Jake and Neytiri's relationship, another planet might make people miss the familiar faces. And if sequels have Na'vi spacetravel, that would be a little cheesy, but maybe it could work?? well I really don't know, I just hope more of Pandora will be explored because aftre all, there is an really large body of water seen in the movie which could mean more epic creatures for Jake to bond with. Now that I think of it, I would really like to see some marine life in Pandora, that would be sweet.